METHOD FOR PRODUCING AN OPTICALLY VARIABLE SECURITY ELEMENT

Description

[0001] The invention relates to a method for producing an optically variable security element.

[0002] Data storage media, such as valuables or identification documents, as well as other valuable items such as branded goods, are often provided with security elements for security purposes. These elements allow verification of the authenticity of the data storage media and also serve as protection against unauthorized reproduction. These security elements can, for example, take the form of a security thread embedded in a banknote, a cover foil for a banknote with a hole, an applied security strip, a self-supporting transfer element, or even a feature area printed directly onto a valuable document.

[0003] Security elements with a viewing-angle-dependent or three-dimensional appearance play a special role in authenticity assurance, as these cannot be reproduced even with the most modern copying machines. For this purpose, the security elements are equipped with optically variable elements that convey a different image impression to the viewer at different viewing angles, for example, displaying a different color or brightness impression and / or a different graphic motif depending on the viewing angle. In the prior art, optically variable effects include, for example, motion effects, pump effects, depth effects, or flip effects, which are realized using holograms, microlenses, or micromirrors.

[0004] EP 1 879 154 A2 discloses a method for producing a security element for a security paper or value document comprising a substrate provided with a two-layer coating. The method comprises the steps of applying a first layer to the substrate, applying at least one second layer to the first layer, wherein the first layer is not fully cured prior to applying the second layer, embossing at least one layer of the coating, and curing the coating.

[0005] The document WO 2014 / 060089 A2 relates to an optically variable surface pattern with a carrier which has a first and a second surface region, wherein the two surface regions are designed such that the first surface region presents a curved-appearing first view in a first solid angle range and the second surface region presents a curved-appearing second view in a second solid angle range which is different from the first solid angle range.

[0006] From the publication WO 2014 / 121908 A1, an optically variable surface pattern is known which has two subregions with reflection elements, wherein the reflection elements of the first subregion, on the one hand, and the reflection elements of the second subregion, on the other hand, reflect incident light in different reflection directions. The first subregion is covered with a first translucent color layer such that, when the viewing angle at which the viewer views the optically variable surface pattern is changed, a viewer sees the first subregion glowing in a first color upon reaching a first viewing angle and the second subregion glowing in a second color different from the first color upon reaching a second viewing angle.

[0007] In DE 10 2014 001842 A1, a layer containing metal pigments and arranged on a first embossed structure is embossed so that the metal pigments of the layer are aligned at the bottom along the first embossed structure and at the top along the second embossed structure. In EP 3 466 711 A1, a liquid crystal layer is applied to a lacquer layer embossed with a first alignment structure, into which a second alignment structure is introduced, so that the liquid crystal layer appears different from both sides. US 2015 / 352887 A1 also provides a layer with two different structures for viewing from different sides. The document shows the preamble of claim 1.

[0008] Based on this, the invention is based on the object of providing a simple and cost-effective method for producing counterfeit-proof and visually attractive optically variable security elements. In particular, the method should enable security elements with two or more different appearances or effects in different colors to be produced with a few work steps. Furthermore, the security elements should ideally be able to be produced with a thin layer to facilitate their incorporation or application into security and valuable documents.

[0009] This object is achieved by the features of the independent claim. Further developments of the invention are the subject of the dependent claims.

[0010] According to the invention, in order to achieve the stated object, a method for producing an optically variable security element is provided that B) a carrier is provided, the surface area of ​​which defines a z-axis perpendicular thereto, A1) a first embossing lacquer layer is applied to the carrier in a surface area, wherein a transparent carrier is provided as the carrier or the carrier is removably connected to the first embossing lacquer layer, P1) a first relief structure is embossed into the first embossing lacquer layer, A2) a second, colored embossing lacquer layer is applied to the first embossing lacquer layer, wherein the color effect of the second embossing lacquer layer differs from the color effect of the first embossing lacquer layer, wherein the first relief structure is partially covered by the second, colored embossing lacquer layer and partially not covered, P2) a second relief structure different from the first relief structure is embossed into the second embossing lacquer layer,such that the first relief structure and the second relief structure are arranged in the z-direction at different heights relative to the carrier, and M) a coating is applied to the second relief structure and to an uncovered portion of the first relief structure, so that, when viewing the security element from the side of the first embossing lacquer layer, a first color impression is created by the combination of the color effects of at least the first embossing lacquer layer and the color coating, and a second, different color impression is created by the combination of the color effects of at least the first embossing lacquer layer, the second embossing lacquer layer and the color coating.

[0011] The first and / or second embossing lacquer layer are preferably applied in steps A1) and A2) respectively by screen printing, offset printing, flexographic printing, or gravure printing. The embossing lacquer of the first and / or second embossing lacquer layer can, in particular, be a UV lacquer, a thermoplastic lacquer, or a so-called dual-cure system, i.e., a combination of a UV lacquer and a thermoplastic lacquer. The second embossing lacquer layer is advantageously applied in register with the first relief structure in step A2).

[0012] After the embossing steps P1) and P2), the first and second embossing lacquer layers are cured in advantageous embodiments, particularly when a UV lacquer or a dual cure system is used.

[0013] In step M, the coating is applied directly to the two embossing lacquer layers. In the context of this description, the phrase "apply to" does not otherwise exclude the presence of intermediate layers between the applied layer and the target object. For example, other layers may have already been applied to the carrier before the first embossing lacquer layer is applied to the carrier in step A1), such as a translucent color coating. The first embossing lacquer layer is then applied to the carrier provided with this color coating. The color coating can be applied both to the side of the first embossing lacquer layer and to the opposite side of the carrier.

[0014] In step M, the coating is applied simultaneously to the first and (the free portion of) the second relief structure. In a coated area, the applied coating is preferably a full-surface coating.

[0015] In an advantageous further development, the (preferably full-surface) coating is provided with recesses after step M). For this purpose, preferably either before step M), a wash ink is printed onto the first and / or second embossing lacquer layer and the wash ink is washed out together with the coating after step M), or after step M), a resist lacquer is applied to the colour coating and the coating is removed in the areas not provided with resist lacquer by an etching step.

[0016] Instead of the resist mentioned above, an optionally colored photoresist can also be applied first over the entire surface and then exposed in sections. Depending on the resist used, the exposed or unexposed areas will then dissolve in the etching bath, releasing the underlying coating while the coating areas covered by the photoresist remain protected from the etching.

[0017] The recesses in the coating are preferably in the form of drawings, patterns, or coding. They advantageously represent negative markings, for example, negative writing, which is particularly visible when the security element is viewed through transmitted light. The recesses or negative markings can generally be placed anywhere on the security element. Depending on their placement and product structure, the recesses or negative markings can create different color impressions. Transparent negative markings are possible, i.e. negative markings that are neither covered by a translucent color nor by metallization. Colored negative markings can also be created, in which the negative markings are covered by at least one translucent color.

[0018] The coating applied in step M) is also referred to herein as a color coating (unless it is clearly transparent). The coating applied in step M) is preferably formed by a metallization (colored or achromatic) or a thin-film structure containing a metal layer. The metallization can, for example, be a layer of aluminum, silver, or an alloy, such as copper and aluminum. Suitable thin-film structures include, in particular, color-shifting thin-film structures, in particular with an absorber-dielectric-absorber or reflector-dielectric-absorber as a layer sequence, for example with silicon and aluminum or chromium sublayers.

[0019] The color coating can also be formed by a translucent paint with a metallic mirror coating, for example, made of aluminum. A luminescent paint, especially a fluorescent paint with a metallic mirror coating, can also be considered as a color coating. Finally, the color coating can also be formed by a nanoparticle paint, such as gold-blue particles, various effect pigments, color-shifting pigments, or supersilver.

[0020] The term "color" typically distinguishes between chromatic colors and achromatic colors, with chromatic colors being characterized not only by their brightness but also by their hue and saturation. Achromatic colors include white, black, and gray, and silvery metallic colors, such as the color of a reflective aluminum or silver coating, are also considered achromatic colors for the purposes of this application.

[0021] To include colorless layers, this description further distinguishes between "color" and "color effect," whereby the more general term "color effect" encompasses both color and colorlessness. A colored or colored layer is a layer with the color effect of a chromatic color (e.g., a red laser-like layer) or an achromatic color (e.g., a silvery-lustrous aluminum layer). Although a colorless layer has no color, its colorlessness nevertheless defines a color effect.

[0022] The term "color impression" is ultimately used for the overall color impression created by one or more layers. Thus, the layers (in the uncovered but coated portion) create a first color impression, which results from the combination of the color effect of at least the first embossing lacquer layer and the color effect of the color coating. A covered portion creates a second, different color impression through the color effects of at least the first embossing lacquer layer, the second embossing lacquer layer, and the color coating. Specifically, for example, the combination of a red translucent layer (red color effect) with a deposited metallization (achromatic color effect) creates a shiny red color impression, or the combination of a blue translucent layer (blue color effect) with a transparent colorless layer (colorless color effect) and a deposited metallization (achromatic color effect) creates a shiny blue color impression.

[0023] In the following, the portion of the first relief structure covered by the second embossing lacquer layer is sometimes referred to for simplification as the overlapping area. As will be described in more detail later for various embodiments, a covered portion can be a surface area or can be present as raster elements within a surface area. In a security element, preferably, several covered portions can also be present.

[0024] In a preferred embodiment, the first embossing lacquer layer is colorless, while the second embossing lacquer layer is colored with a translucent color or achromatic color. However, other designs are also advantageous, in which one or both embossing lacquer layers are colored with a translucent color, a luminescent color, or a nanoparticle color. The only requirement is that the color effects of the first and second embossing lacquer layers differ from one another.

[0025] In an advantageous development of the method, it is provided that a further color coating, in particular a translucent color coating, is applied to the side of the carrier opposite the embossing lacquer layers, or between the carrier and the first embossing lacquer layer. This makes it possible to create a variety of color combinations when viewing the security element. In particular, a first color impression results in the uncovered, coated portion through the combination of the color effects of the further color coating, the first embossing lacquer layer, and the coating already mentioned above, and a second color impression results in the covered portion (overlap area) through the combination of the color effects of the further color coating, the first embossing lacquer layer, the second embossing lacquer layer, and the coating already mentioned above.

[0026] In a particularly preferred embodiment, the first and / or second relief structure are formed by micromirror arrangements with directional micromirrors, in particular with flat mirrors, concave mirrors, and / or Fresnel-type mirrors. The lateral dimensions of the micromirrors are advantageously below 20 µm, preferably below 10 µm.

[0027] The first and second color impressions are perceptible to the viewer separately from one another, in particular depending on the viewing angle and / or separately from one another in certain regions. The micromirrors of the first and / or second relief structure are preferably configured to generate only one of the two color impressions for the viewer in an effect region, depending on the viewing angle. The micromirrors of the first and / or second relief structure are alternatively or additionally configured to generate the two color impressions in two (adjacent or separate) surface regions. In the present relief structures, each of the micromirrors is aligned with a predetermined spatial orientation (azimuth angle and inclination angle). The orientation is adapted to a motif and to a viewing angle dependence of the motif.A viewing angle dependency can cause a movement effect, a three-dimensional impression or a change in the motif for a motif in the (respective) surface area.

[0028] Advantageously, a transparent carrier is provided as the carrier, or the carrier is removably bonded to the first embossing lacquer layer to enable viewing of the security element from the side of the first embossing lacquer layer. With a transparent carrier, viewing can take place through the carrier; a non-transparent carrier must be removed for viewing from the side of the first embossing lacquer layer, for example, after the security element has been transferred to a target substrate. The transparent carrier is advantageously colorless, but it can also be tinted to create an additional color effect.

[0029] In an advantageous variant of the invention, the second embossing lacquer layer is applied at least in a partial area in the form of a regular or irregular grid with grid elements and grid spaces, wherein the dimensions of the grid elements and / or grid spaces are at least in one direction between 20 µm and 200 µm, preferably between 60 µm and 150 µm, in particular between 80 µm and 120 µm.

[0030] In an advantageous embodiment, the grid elements and grid spaces of the grid have the same shape and preferably also the same size. The grid elements and / or the grid spaces can in particular be formed by strip-shaped, square, triangular or other polygonal elements, but can also have irregular shapes. The grid itself can be regular, i.e. have a regular arrangement of grid elements and grid spaces, but can also be an irregular grid, for example a stochastic grid in which the grid elements and / or grid spaces have irregular spacings and / or sizes and / or shapes. The area coverage of the grid by the grid elements is advantageously between 30% and 70%, preferably between 40% and 60%, in particular approximately 50%.

[0031] Alternatively or in addition to the aforementioned grid, an effect area is formed in which an uncovered portion forms (at least) a first surface area with the first relief structure, and a covered portion forms (at least) a second surface area with the second relief structure. Advantageously, the dimensions of the surface areas are above the resolution limit of the naked eye, so that each surface area can be recognized without aids.

[0032] Alternatively or in addition to the mentioned grid and / or the mentioned surface areas, an effect area is formed in which the second embossing lacquer layer is applied in partial areas which have lateral dimensions of more than 140 µm, and / or in which the second embossing lacquer layer is applied with recesses which have lateral dimensions of more than 140 µm. The lateral dimensions of at least one partial area and / or at least one recess are preferably more than 250 µm, preferably more than 500 µm and in particular more than 1 mm. In the case of micromirror arrangements or other relief structures which are formed from small relief elements, the partial areas or recesses of the effect area therefore typically extend over many micromirrors or relief elements. The mentioned dimensions can depend on the partial areas orRecesses are only exceeded in one lateral direction, but the recesses are advantageously larger than the specified dimensions in every lateral direction. Particularly advantageous are the dimensions that are above the resolution limit of the naked eye, so that the surface area of ​​the partial areas or recesses can be recognized without any aids.

[0033] The two relief structures advantageously provide a color change for an unchanged motif, depending on the viewing angle, or provide a color change along with a motif change. The motifs of the two relief structures can differ, in particular, in terms of shape (e.g., head, apple, or tail), movement (static to moving or moving to static, with linear, rotating, and / or pumping movement), and / or dimensionality (2D to 3D, or different three-dimensionality with a positively or negatively curved appearance, or floating in front of or behind a plane).

[0034] In an advantageous embodiment, the first relief structure creates a first motif that is visible from a first viewing angle range with a first color impression resulting from the combination of the color effects of at least the first embossing lacquer layer and the color coating, and the second relief structure creates a second motif that is visible from a second viewing angle range with a second, different color impression resulting from the combination of the color effects of at least the first embossing lacquer layer, the second embossing lacquer layer, and the color coating, wherein the first and second viewing angle ranges do not overlap. When tilted, the security element then displays a binary color and effect change without an overlap region.Advantageously, the two viewing angle ranges are adjacent to each other or are separated by an angular distance of only a few degrees, so that the corresponding image impressions skip practically seamlessly for the viewer.

[0035] In another, equally advantageous embodiment, it is provided that the first relief structure creates a first movement motif with a first color impression and the second relief structure creates a second movement motif with a second, different color impression, wherein the first and second movement motifs move offset from one another or move against one another when the security element is tilted and thereby cross in an overlapping position in which both movement motifs are visible and / or move successively through the same part of the common area. Here, too, the first color impression is created by the combination of the color effects of at least the first embossing lacquer layer and the color coating, and the second color impression is created by the combination of the color effects of at least the first embossing lacquer layer, the second embossing lacquer layer, and the color coating.

[0036] The proposed process allows the production of security elements of the type mentioned above in only a few steps. The described layer structure also allows for the production of security elements with a total thickness of less than 45 µm, which are ideal for use in banknotes and other valuable documents.

[0037] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0038] They show: Fig. 1 a schematic representation of a banknote with two security elements according to the invention, Fig. 2 schematically a section of the first security element of the Fig. 1 in cross-section, Fig. 3in (a) to (d) intermediate steps in the manufacture of the security element of the Fig. 2 , Fig. 4in (a) to (d) some concrete advantageous embodiments of the grid of the embossed structure of the security element of Fig. 2 in plan view, Fig. 5 schematically shows a section of the second security element of the Fig. 1 in cross-section, Fig. 6in (a) to (f) intermediate steps in the manufacture of the security element of the Fig. 5 , and Fig. 7 a modification of the security element of the Fig. 2 in cross section.

[0039] The invention will now be explained using the example of security elements for banknotes. Figur 1 shows a schematic representation of a banknote 10 with two optically variable security elements 12 and 62, each in the form of an adhesively bonded transfer element. It is understood, however, that the invention is not limited to transfer elements and banknotes, but can be used for all types of security elements, for example, labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards, and the like. For banknotes and similar documents, in addition to transfer elements, security threads or security strips, for example, can also be considered. The two security elements 12, 62 of the Fig. 1 are themselves very flat, but still give the viewer a three-dimensional impression.

[0040] In addition to the three-dimensional appearance, the first security element 12 displays a binary color and effect change when the banknote 10 is tilted. From a first viewing direction, a first motif 14-A appears, seemingly bulging out of the plane of the banknote 10, for example, a curved representation of the value "10," with a first, for example, shiny silver color impression. From a second viewing direction, a second motif 14-B appears, seemingly bulging out of the plane of the banknote 10, for example, a curved representation of a coat of arms with a second color impression, for example, a shiny red color impression.

[0041] When the banknote 10 is tilted 16 or the viewing direction changes accordingly, the appearance of the security element 12 suddenly jumps from the first to the second appearance, or when tilted back, from the second to the first appearance. The change in motif and color occurs simultaneously and without an intermediate or transitional stage in which both motifs or colors would be visible simultaneously or one motif would be visible in the color of the other motif. The appearance therefore jumps seamlessly between two appearances 14-A, 14-B and is therefore referred to as a binary color and effect change.

[0042] The special structure and the inventive manufacture of the first security element 12 will now be described with reference to the Figuren 2 and 3 explained in more detail, whereby Fig. 2 schematically shows a section of the security element 12 applied to the banknote 10 in cross section and Fig. 3 shows various intermediate steps in the production of the security element 12.

[0043] The security element 12 contains a flat, transparent, colorless carrier 18, the surface area of ​​which defines an xy plane and a z-axis perpendicular thereto. Arranged on the carrier 18 is a multicolored reflective surface area which contains an embossed structure area 25 with two nested micromirror embossments 24, 34 at two different heights. A first embossed area 24 is provided by micromirror embossments whose base areas lie at a height H 1 above the carrier 18. A second embossed area 34 is provided by micromirror embossments whose base areas lie at a height H 2 > H 1 above the carrier 18. The height as well as the direction of the positive z-axis are always measured starting from the carrier 18. Since the security element 12 is designed to be viewed from the underside, i.e. the side of the carrier 18, the z-axis extends Fig. 2 downwards away from the wearer.

[0044] The micromirror embossings 24, 34 (hereinafter also referred to as micromirror arrangements) each contain a plurality of micromirrors inclined relative to the xy plane, the local angles of inclination of which are selected such that the relief structures of the micromirror embossings 24, 34, in interaction with the color effects of the embossing lacquer layers 22, 32 and the color effect of a uniform color coating 26, produce a desired optical appearance.

[0045] Specifically, the inclination angles of the micromirrors in the exemplary embodiment are selected such that the micromirror arrangement 24 generates the curved representation of the value "10" in a viewing angle range of +5° to +20° relative to the surface normal (viewing position 40-A), and the micromirror arrangement 34 generates the curved representation of the coat of arms in a viewing angle range of -5° to -20° (viewing position 40-B). The micromirrors of the micromirror embossments 24, 34 themselves have a lateral dimension of 10 x 10 µm 2< and a maximum height h of 3.5 µm in the exemplary embodiment. The height offset ΔH = H 2 - H 1 relative to the base surfaces can be, for example, ΔH = 6 µm.

[0046] As in connection with Fig. 3 As explained in more detail, the micromirror arrangements 24, 34 are produced by embossing two different embossing lacquer layers 22, 32 with different color effects. While the embossing lacquer layer 22, in which the micromirror arrangement 24 is embossed, is transparent and colorless, the embossing lacquer layer 32, in which the micromirror arrangement 34 is embossed, is colored a translucent red. Both micromirror arrangements 32, 34 are provided with a uniform color coating 26, which in the exemplary embodiment is formed by a metal coating, specifically by a thin, vapor-deposited aluminum layer, which has a silvery metallic and thus achromatic color effect.

[0047] The desired visual contrast of the micromirror arrangements 24, 34 from the viewing positions 40-A or 40-B of the observer 40 is created by the interaction of the different color effects of the embossing lacquer layers 22, 32 with the color effect of the uniform color coating 26.

[0048] The two micromirror arrangements 24, 34 are in the embodiment of the Fig. 2 nested in the entire surface area of ​​the security element 12 in the form of a regular grid 50, wherein in the first grid areas 52 only the micromirror embossings 24 of height level H 1 are present, while in the complementary second grid areas 54, the overlap area, the second embossing lacquer layer 32 with the micromirror embossings 34 at height level H 2 are additionally present and are optically effective. Specifically, the grid areas 52, 54 in the exemplary embodiment form a checkerboard pattern in which each field, i.e. each grid area 52, 54 has a dimension of 100 µm x 100 µm. Since the micromirrors are generally significantly smaller, here for example having an edge length of only 10 µm, the grid 50, unlike in the simplified schematic representation of the Figuren 2 and 3, generally do not coincide with the grid of the micromirrors of the micromirror arrays 24, 34.

[0049] Overall, the described arrangement results in the desired appearance. Since the carrier 18 and the first embossing lacquer layer 22 are transparent and colorless, the micromirror arrangement 24 with the silvery metallic appearance of the aluminum layer 26 is visible from the viewing position 40-A, which shows the curved representation 14-A of the value number "10." Due to the red translucent coloring of the second embossing lacquer layer 32 and the backing of the second embossing lacquer layer with the aluminum layer 26, the coat of arms 14-B appears with a shiny red appearance from the viewing position 40-B.

[0050] The inventive production of the security element 12 will now be described with reference to Figur 3 described in more detail, with (a) to (d) each showing intermediate steps in the manufacture of the security element.

[0051] First, with reference to Fig. 3(a) A transparent carrier 18, for example, a transparent, colorless PET film, is provided and provided with a first, transparent, colorless embossing lacquer layer 22. Using an embossing tool (not shown), the micromirror embossing 24, which creates the representation 14-A of the value "10," is embossed into the first embossing lacquer layer 22. When using a UV embossing lacquer, the embossing lacquer layer 22 is subsequently cured.

[0052] A second, translucent red colored embossing lacquer layer 32 is then printed onto the first embossing lacquer layer 22 in a regular grid 50 using a printing cylinder (not shown), as in Fig. 3(b) The grid 50 is formed in the form of grid elements 54 and grid spaces 52, and corresponds, for example, to the checkerboard pattern described above with field dimensions of 100 µm x 100 µm. In this exemplary embodiment, the grid elements 54 create the overlapped portion or overlap area mentioned above, in which the second embossing lacquer layer 32 is applied to the first embossing lacquer layer 22.

[0053] Subsequently, the second embossing lacquer layer 32 is provided with the micromirror embossing 34, which creates the coat of arms representation 14-B, using an embossing tool (not shown), as in Fig. 3(c) shown. When using a UV embossing varnish, the embossing varnish layer 32 is subsequently cured.

[0054] A full-surface metal coating 26, for example an aluminum layer, is then applied to the overall relief structure 25 thus formed, which is formed by the first relief structure 24 of the first embossing lacquer layer 22 and the second relief structure 34 of the second embossing lacquer layer 32, as shown in Fig. 3(d) Finally, the structural side of the metallized overall relief structure 25 is provided with a lacquer coating 48 and, if necessary, further coatings, thereby completing the security element 12.

[0055] A key advantage of the manufacturing process according to the invention is the very small number of required work steps compared to conventional processes. The proposed layer structure also results in very thin product thicknesses of less than 45 µm, which is particularly important for the use of security elements in banknotes and other valuable documents. Furthermore, the security elements can also be easily provided with transparent or colored negative markings using the described process, as explained in more detail elsewhere.

[0056] Figur 4 shows some concrete advantageous embodiments of the grid 50 of the second embossing lacquer layer 32 in a top view. The grid elements 54 are each hatched, and the grid spaces 52 are each shown without hatching. Figur 4(a) shows a grid 50 as it is in Figuren 2 and 3is used, in which the grid elements 54 and grid spaces 52 form a checkerboard pattern. The dimensions of the grid areas are advantageously between 20 x 20 µm 2< and 140 x 140 µm 2< , in particular between 20 x 20 µm 2< and 60 x 60 µm 2< , the area coverage is 50%. If an area coverage deviating from 50% is to be produced, some of the grid elements 54 can be omitted, or some of the grid spaces 52 can be occupied with grid elements.

[0057] In this embodiment, as well as in the designs described below, the area coverage of the grid with grid elements 54 is preferably between 30% and 70%, in particular between 40% and 60%. The brightness of the generated appearances can be adjusted as desired by adjusting the area coverage of the first and second grid areas.

[0058] Figur 4(b) shows a grid 50 with alternating strip-shaped grid elements 54 and grid spaces 52. The width of the grid areas is advantageously between 20 µm and 140 µm, in particular between 20 µm and 60 µm. The length of the grid areas is arbitrary and can be several millimeters or even several centimeters. The area coverage can be easily adjusted via the relative width of the grid elements and grid spaces.

[0059] The grid elements and grid spaces can also have other polygonal shapes or irregular shapes. For example, Fig. 4(c) a configuration in which the grid elements 54 and grid spaces 52 of the grid 50 are formed by triangles. In the grid 50 of the Fig. 4(d) The grid elements 54 and grid spaces 52 are formed by irregular shapes. The grid elements and / or grid spaces can form a coherent structure, such as in Fig. 4(d) for the grid spaces 52.

[0060] Returning to the presentation of the Fig. 1 The second security element 62 transferred to the banknote 10 is itself very flat, but nevertheless gives the viewer the three-dimensional impression of a motif 64 that appears to bulge out from the plane of the banknote 10 and appears with a first color impression. The motif 64 can, for example, represent a value number, a portrait, or another graphic motif. Within the motif 64 with the first color impression, a movement effect with a second color impression is visible in a partial area 66. For example, when the banknote 10 is tilted, a light bar can move up and down along the partial area 66, creating a so-called rolling bar effect. A key special feature is that the areas with different color impressions (first and second color impressions) and different effects (three-dimensional motif or moving bar) are precisely aligned with one another.This registration is therefore also referred to as color-to-effect registration.

[0061] Additionally, the security element 62 contains a negative inscription 68 in the form of the value number "10," which is formed by a transparent portion of the security element 62. If the security element 62 is arranged over an opaque area of ​​the banknote 10, the surface of the banknote, for example, the white banknote paper, becomes visible there. If the security element 62 is arranged over a window area of ​​the banknote, the negative inscription 68 forms a transparent see-through area in the security element 62, which illuminates brightly when viewed through transmitted light.

[0062] The special structure and the inventive manufacture of the security element 62 will now be described with reference to the Figuren 5 and 6 explained in more detail, whereby Fig. 5 schematically shows a section of the security element 62 applied to the banknote 10 in cross section and Fig. 6 shows various intermediate steps in the production of the security element 62.

[0063] The security element 62 is similar to that used in connection with Fig. 2 The security element 62 is constructed from the previously described security element 12, so that corresponding elements are each designated by the same reference numerals. The security element 62 contains a flat, transparent, colorless carrier 18, the surface area of ​​which defines an xy plane and a z axis perpendicular thereto. Arranged on the carrier 18 is a multicolored reflective surface area containing an embossed structure area with micromirror embossments with two different height levels.

[0064] As in Fig. 2 A first embossed area 24 is provided by micromirror embossments, the base areas of which are located at a height H 1 above the carrier 18, while a second embossed area is provided by micromirror embossments 34, the base areas of which are located at a height H 2 > H 1 above the carrier 18. The micromirror embossments or micromirror arrangements 24, 34 contain, as in the embodiment of the Fig. 2 in each case a plurality of micromirrors inclined relative to the xy plane, the local angles of inclination of which are selected such that the relief structures of the micromirror embossings 24, 34, in interaction with the color effects of the embossing lacquer layers 22, 32 and the color effect of a uniform color coating 26, produce a desired optical appearance.

[0065] Specifically, the angles of inclination of the micromirrors in the exemplary embodiment are selected such that the micromirror arrangements 24, 26 create the curved three-dimensional impression of the motif 64 and the rolling bar effect of the partial area 66. The sizes and heights of the micromirrors can be selected as in the exemplary embodiment of the Fig. 2 be elected.

[0066] While the embossing lacquer layer 22, in which the micromirror arrangement 24 is embossed, is transparent and colorless, the embossing lacquer layer 32, in which the micromirror arrangement 34 is embossed, is colored translucent blue. Both micromirror arrangements 32, 34 are provided with a uniform color coating 26, which in the embodiment of the Fig. 5 is formed by a metal coating, specifically by a thin, vapor-deposited silver layer, which has a silvery metallic and thus achromatic color effect.

[0067] The desired visual contrast of the micromirror arrangements 24, 34 from the different viewing positions of the observer is created by the interaction of the different color effects of the embossing lacquer layers 22, 32 with the color effect of the uniform color coating 26.

[0068] The two micromirror arrangements 24, 34 are in the embodiment of the Fig. 5 in the surface area of ​​the security element 62, each arranged directly adjacent to one another. The partial area 66 is formed, for example, by a 5 mm wide and 2 cm long curved strip within a 2.5 x 2.5 cm 2< surface area 64. While the observer in the partial area 66, which represents the above-mentioned overlap area, looks through the translucent blue embossing lacquer layer 32 onto the micromirror arrangement 34 with the silver layer 26 located at height level H 2, the visual impression in area 64, i.e. outside the overlap area 66, is determined by the micromirror arrangement 24 located at height level H 1 and thus solely by the color effect of the silver layer 26.

[0069] In area 64, the observer therefore perceives the silvery, shiny motif 64 created by the micromirror arrangement 24, while within sub-area 66, the blue-metallic rolling bar effect appears, in which a blue-reflective bar appears to move back and forth along the curved stripe when the banknote 10 is tilted. Since the height difference between the two micromirror arrangements 24, 34 is in the range of a few micrometers, it is imperceptible to the observer, so that the two differently colored motifs and the different effects 64, 66 appear to be arranged next to one another in exact registration.

[0070] The security element 62 also has a smaller sub-area 68 in the area 64, which is shaped like the value number "10" and in which the ink coating 26 is left out. Due to the lack of an ink coating and the transparency of the other layers present in sub-area 68, a negative mark is created in the security element 62. Depending on the arrangement of the security element, sub-area 68 forms a transparent window in the banknote or it provides a view of the banknote's surface.

[0071] The inventive production of the security element 62 will now be described with reference to Figur 6 described in more detail, with (a) to (f) each showing intermediate steps in the manufacture of the security element.

[0072] First, with reference to Fig. 6(a) A transparent carrier 18, for example, a transparent, colorless PET film, is provided and provided with a first, transparent, colorless embossing lacquer layer 22. Using an embossing tool (not shown), the micromirror embossing 24, which creates the motif 64 of the security element 62, is embossed into the first embossing lacquer layer 22. When using a UV embossing lacquer, the embossing lacquer layer 22 is subsequently cured.

[0073] A second, translucent blue colored embossing lacquer layer 32 is printed onto the first embossing lacquer layer 22 using a printing cylinder (not shown) in the desired overlap area 66 of the running bar, as shown in Fig. 6(b) With reference to Fig. 6(c) The second embossing lacquer layer 32 is then provided with the micromirror embossing 34 that creates the rolling bar effect using an embossing tool (not shown). When using a UV embossing lacquer, the embossing lacquer layer 32 is subsequently cured.

[0074] To produce the negative writing, wash ink 70 is printed in the partial areas 68 which are to be subsequently demetallized, as shown in Fig. 6(d) shown.

[0075] A uniform, full-surface metal coating 26, for example the aforementioned silver layer, is then applied to the overall structure thus produced, which is formed by the first relief structure 24 of the first embossing lacquer layer 22, the second relief structure 34 of the second embossing lacquer layer 32 present in the overlapping region 66 and the wash ink 70 printed in the partial regions 68, as shown in Fig. 6(e) shown.

[0076] Subsequently, the wash ink 70 is washed out together with the part of the metal coating 26 lying on the wash ink and thereby the Fig. 6(f) Finally, the structural side of the partially metallized relief structure is provided with a lacquer coating 48 and, if necessary, further coatings, thus completing the security element 62. The color variety of the appearances of the two micromirror embossings can be further increased within the scope of the invention. For illustration, Fig. 7 a modification of the embodiment of the Fig. 2 , in which both the motif 14-A (value number "10") and the coat of arms motif 14-B appear with a colorful impression. For this purpose, the security element 80, in addition to the Fig. 2 already described elements, a continuous translucent color layer 82 is provided on the side of the carrier 18 facing away from the micromirror embossings 24, 34.

[0077] When viewed, the motif 14-A of the micromirror embossing 24 then appears shiny with a first color due to the combined effect of the color layer 82 and the metallization 26, and the motif 14-B of the micromirror embossing 34 appears shiny with a second color due to the combined effect of the color layer 82, the colored embossing lacquer layer 32 and the metallization 26, which is created by a subtractive color mixture of the colors of the color layer 82 and the embossing lacquer layer 32. If, for example, the embossing lacquer layer 32 is colored translucent cyan and the color layer 82 is colored translucent yellow, the motif 14-A appears with a yellow glossy color and the motif 14-B appears with a green glossy color due to the subtractive color mixture of cyan and yellow.

[0078] Alternatively, the ink layer 82 can also be provided between the carrier 18 and the first embossing lacquer layer 22. Instead of providing an additional ink layer 82, a translucently colored first embossing lacquer layer 22 or a translucently colored carrier film 18 can also be used. These measures can also increase the color variety of the appearances.

[0079] Even if the embodiments have been specifically described with metal layers and translucent colored colors for illustration purposes, it is understood that the other colors mentioned above can also be used for the color coating 26 and the embossing lacquer layers 22, 32. Bezugszeichenliste

[0080] 10 Banknote 12 First security element 14-A, 14-B Bulging motifs 16 Tilt direction 18 Carrier 22 First embossed lacquer layer 24 First embossed area 25 Overall relief structure 26 Color coating 32 Second embossed lacquer layer 34 Second embossed area 40, 40-A, 40-B Viewer 48 Lacquer coating 50 Grid 52 Grid spaces 54 Grid elements 62 Second security element 64 Bulging motif 66 Partial area, overlap area 68 Negative writing 70 Wash ink 80 Security element 82 Transparent color layer

Claims

1. Method for producing an optically variable security element, wherein B) a carrier (18) of which the surface extent defines a z-axis perpendicular thereto is provided, A1) a first embossing varnish layer (22) is applied to the carrier in a surface region, wherein the carrier provided is a transparent carrier or the carrier is detachably connected to the first embossing varnish layer, P1) a first relief structure (24) is embossed into the first embossing varnish layer (22), A2) a second, coloured embossing varnish layer (32) is applied to the first embossing varnish layer (22), wherein a colour effect of the second embossing varnish layer (32) differs from a colour effect of the first embossing varnish layer (22), and wherein the first relief structure (24) is partially covered by and partially not covered by the second, coloured embossing varnish layer (32), P2) a second relief structure (34) that differs from the first relief structure is embossed into the second embossing varnish layer (32), with the result that the first relief structure (24) and the second relief structure (34) are located at different heights in the z-direction with respect to the carrier (18), and M) a coating (26) is applied to a non-covered portion (52; 64) of the first relief structure (24) and to the second relief structure (34), characterized in that, when the security element is observed from the side on which the first embossing varnish layer (22) is, the combination at least of the colour effects of the first embossing varnish layer (22) and the coating (26) produces a first colour impression, and the combination of the colour effects at least of the first embossing varnish layer (22), the second embossing varnish layer (32) and the coating (26) produces a second, different colour impression.

2. Method according to Claim 1, characterized in that the first and / or the second embossing varnish layer are / is applied by screen printing, offset printing, flexographic printing or gravure printing.

3. Method according to Claim 1 or 2, characterized in that, in step A2), the second embossing varnish layer (32) is applied in register with respect to the first relief structure.

4. Method according to at least one of Claims 1 to 3, characterized in that, after step M), the coating (26) is provided with cutouts, preferably by either - printing a washable ink (70) onto the first and / or the second embossing varnish layer before step M) and washing out the washable ink together with the coating (26) after step M), or - after step M) a resist is applied to the coating (26) and the coating in the regions not provided with resist is removed by an etching step.

5. Method according to at least one of Claims 1 to 4, characterized in that the coating (26) is formed by a preferably chromatic colour coating, in particular by a metallization with a translucent colour layer, a chromatic metallization or a thin-layer structure containing a metal layer.

6. Method according to at least one of Claims 1 to 5, characterized in that the coating (26) is formed by an achromatic coating, in particular by a metallization in the form of an achromatic colour coating, or by a transparent, reflection-increasing layer.

7. Method according to at least one of Claims 1 to 5, characterized in that the first embossing varnish layer (22) is colourless and the second embossing varnish layer (32) is dyed with a translucent chromatic colour or achromatic colour.

8. Method according to at least one of Claims 1 to 7, characterized in that a further colour coating, in particular a translucent colour coating (82), is applied to the opposite side of the carrier (18) to the embossing varnish layers (22, 32), or between the carrier (18) and the first embossing varnish layer (22).

9. Method according to one of Claims 1 to 8, characterized in that the first and / or the second relief structure are / is formed by micromirror arrangements with directed micromirrors, in particular with plane mirrors, concave mirrors and / or Fresnel-like mirrors, wherein the lateral dimensions of the micromirrors are advantageously less than 20 µm, preferably less than 10 µm.

10. Method according to one of Claims 1 to 9, characterized in that the second embossing varnish layer (32) is provided with pattern elements (54) and pattern intermediate spaces (52) in the form of a regular or irregular pattern in at least one subregion, wherein the dimensions of the pattern elements and / or the pattern intermediate spaces at least in one direction are between 20 µm and 200 µm, preferably between 60 µm and 150 µm, in particular between 80 µm and 120 µm.

11. Method according to one of Claims 1 to 10, characterized in that the second embossing varnish layer is applied in subregions (66) that have lateral dimensions of more than 140 µm, and / or in which the second embossing varnish layer is applied with cutouts that have lateral dimensions of more than 140 µm.

12. Method according to Claim 11, characterized in that the lateral dimensions of at least one subregion and / or of at least one cutout are more than 250 µm, preferably more than 500 µm and in particular more than 1 mm.

13. Method according to one of Claims 1 to 12, characterized in that the first and the second colour impression can be perceived separately from one another, in particular can be perceived separately from one another depending on the observation angle and / or in some regions.

14. Method according to one of Claims 1 to 13, characterized in that the two relief structures, depending on the observation angle, provide a colour change for an unchanging motif or provide a colour change together with a motif change, wherein the motifs of the two relief structures differ in particular in terms of the shape, movement and / or dimensionality of the motif.

15. Method according to one of Claims 1 to 14, characterized in that the first relief structure generates a first motif which is visible from a first observation angle range with a first colour impression produced by the combination of the colour effects of the first embossing varnish layer and the colour coating, and in that the second relief structure generates a second motif which is visible from a second observation angle range with a second, different colour impression produced by the combination of the colour effects of the first embossing varnish layer, the second embossing varnish layer and the colour coating, wherein the first and second observation angle ranges do not overlap.

16. Method according to one of Claims 1 to 14, characterized in that the first relief structure generates a first movement motif with a first colour impression and the second relief structure generates a second movement motif with a second, different colour impression, wherein, when the security element is tilted, the first and the second movement motif - move in a manner offset from one another and intersect in an overlap position, in which both movement motifs are visible, and / or - move one after the other through the same part of a common region.